Heat Tracing Systems

What Are Heat Tracing Systems?

Heat tracing systems prevent pipes and process equipment from freezing while maintaining specific temperatures critical for industrial operations.

These systems can be divided into two broad categories: fluid heat tracing and electric heat tracing.

Why Heat Tracing is Critical for Industrial Operations

• Preventing Freeze Damage: Trace heating is a vital element in the reliable operation of pipelines, storage and process vessels throughout the process industry. Anti-frost protection for water pipelines is needed both in the processing industries as well as in commercial and domestic buildings.

• Maintaining Process Temperatures: Of equal importance is the tracing of process pipelines which carry liquids that can be pumped only at temperatures that are well above the freezing temperature of water. For example:

• • Oil and fat lines must be heat traced to maintain viscosity
  • Asphalt and sulfur in the chemical process industry can only be moved through pipelines at specific temperatures
  • Heavy liquids in oil refineries and petroleum processing plants require heating before they can be moved

Viscous fluids become extremely difficult, and sometimes impossible, to pump if they cool below a certain temperature. To avoid this, it is necessary to supply heat to the product to keep it fluid enough to flow without excessive work by the pumps.

Fluid Heat Tracing Systems Explained

How Fluid Heat Tracing Works

Fluid heat-tracing systems utilize heating media at elevated temperatures to transfer heat to a pipeline. The fluid is generally held within a tube or a small pipe that is connected to the pipe being traced.

Why Steam is Popular for Heat Tracing Fluid

Steam has been the original heat-tracing system of choice due to several desirable features:

• High latent heat from vaporization: ideal for heat-transfer applications
• Efficient heating: only a small quantity is required for large heating loads
• Quick response: can heat a line quickly and condense at constant temperature
• Self-flowing: flows to the point of use without pumping
• Safe and available: universally available and non-toxic

When steam is the tracing fluid, the condensate is either returned to the boiler or dumped.

Also read: Steam Tracing for Pipe Protection

Organic Heat-Transfer Fluids

If an organic heat-transfer fluid is employed, it is returned to a heat exchanger for reheating and recirculation. In general, heating of tracing fluids can be provided by:

• Waste heat from a process stream
• Burning of fossil fuels
• Steam
• Electricity

Electric Heat Tracing Systems Explained

How Electric Heat Tracing Works

Electric heat-tracing systems convert electric power to heat and transfer it to the pipe and its contained fluid. The majority of commercial electric heat-tracing systems in use today are of the resistive type and take the form of cables placed on the pipe.

When current flows through the resistive elements, heat is produced in proportion to the square of the current and the resistance of the elements to current flow. Other specialized electric tracing systems make use of impedance, induction, and skin conduction effects to generate and transfer heat.

Choosing Between Steam Tracing and Electric Tracing

Key Considerations

The amount of heat energy required to maintain the desired temperatures may influence the type of tracing to be used. (Methods for calculating heat load are outside the scope of this discussion).

The choice of tracing method will usually lie between steam, hot liquid, or electrical tracing.

Hot water is often used in the food industry where relatively low temperatures are desirable, such as keeping chocolate in a molten state.

Hot oils are occasionally used in chemical processing, particularly when high temperatures are needed.

For the majority of applications, however, the choice falls between steam tracing and electrical tracing.

Steam Tracing vs. Electric Tracing: Making the Right Choice

Many articles discuss the benefits of using steam versus electricity (or the other way around) for tracing applications. A valid case can probably be made for either, depending on the method being promoted by the particular author.

These promotional articles have generally been based on strictly economic considerations which represent only part of the story. The practical advantages of each system go beyond simple cost calculations and should consider:

• Initial installation costs
• Operating and maintenance requirements
• Heat transfer efficiency
• Safety considerations
• Application-specific requirements

Source: Fluid Controls Institute (FCI) Tech Sheet #ST 102

Three Types of Steam Tracing Methods

Steam tracing can be used to prevent freezing, solidification, or separation-particularly important in lines that cannot be flushed, blown down, or drained while the process unit or equipment is on stream.

In its simplest terms, steam tracing consists of applying steam to the areas requiring protection by means of tubing or small-sized pipe that follows the contours of the product line or equipment to provide the required level of heat.

1. External Steam Tracing

How It Works: Pipe or tubing of small-bore carrying steam is either wrapped around the product line or vessel, or parallel runs are placed outside the product line, with heat transfer taking place through the pipe wall.

Best Practices for External Tracing:

• Multiple tracer lines: If more than one tracer line is used on the outside of the pipe, they should be on different traps. This ensures that some heating will still take place if one trap becomes clogged or stuck in the closed position.
• Feed direction: Two parallel tracer lines along a product pipe should, if possible, be fed in opposite directions so that a drop in temperature along the tracer lines will cancel each other out and maintain a more uniform total effect on the product line.
• Insulation considerations: When insulation is placed over the traced line, it requires larger diameter insulation (often 1″ larger or more than normally would be used). This often leads to odd sizes being required, which increases the price of the insulation.
• Heat control: If there is too much heat transfer to the product, it is usual to place some blocking between the tracer and the product line, or place a thin layer of insulating paper between them.
• Proper fastening: It is essential that the tracer be spaced uniformly along long pipe runs and fastened properly to permit some movement without danger of it working loose or pulling away from the product line.

2. Internal Steam Tracing

How It Works: The steam tracer line runs inside the product pipe itself, often coiled within the product line for maximum heat transfer.

3. Jacketing (Steam Jacket)

How It Works: The steam heating is provided from outside the product line within a jacket surrounding the pipe, providing much more heating surface than either of the other two methods.

Ambient Sensing Steam Tracing Valves

A hybrid solution for temperature control is the Ambient Sensing Steam Tracing Valve. These valves sense the temperature of the air around the actuator and stroke the valve open as temperature approaches the set point. They are generally used for the steam tracing of oil, gas, or chemical lines that must be kept from freezing.

Conclusion: Selecting the Right Heat Tracing Solution

Heat tracing systems are essential for protecting pipelines, valves, instruments, and process equipment from low temperatures that can cause freezing, solidification, or separation. Whether you choose fluid-based or electric heat tracing depends on:

• Your specific heat load requirements
• Operating temperature needs
• Maintenance capabilities
• Budget considerations
• Safety requirements
• Available utilities

Steam tracing remains one of the most practical methods for providing supplemental heat to process lines, protecting products, instruments, valves, and automatic controls from low process-fluid temperatures. Understanding the three types of steam tracing methods-external, internal, and jacketing-helps you select the optimal solution for your application.

For expert guidance on selecting the right heat tracing system for your industrial application, contact our technical team today.